Difference Between ALS and PLS (With Table)

Difference Between ALS and PLS (With Table)

ALS and PLS are diseases that affect the nervous system in the modern world. It is important to be aware of these diseases and their differences.

Both of these diseases take place in people over 40 years of age. However, it is possible to be diagnosed with either of these diseases at any age.


The main difference between ALS (Amyotrophic Lateral Sclerosis) and PLS (Primary Lateral Sclerosis) is that Amyotrophic Lateral Sclerosis affects the upper and lower motor neurons.
On the other hand, Primary Lateral Sclerosis affects only the upper motor neurons alone.

ALS, a type of progressive neuron system disease, is known to be a very fatal disease. No cure for Amyotrophic Lateral Sclerosis has been found to date. The cause of most cases of this neuron disease is also unknown.

PLS, a progressive neuron system disease, is known to be a less fatal version of ALS. Some scholars even argue against PLS being a separate disease and instead say that it is simply a less severe version of ALS, that may lead to ALS in the future.

Comparison Table Between ALS and PLS

Comparison ParameterAmyotrophic Lateral Sclerosis Primary Lateral Sclerosis
Affected NeuronsALS affects both upper and lower motor neurons.PLS affects the upper motor neurons alone.
Life ExpectancyPLS is not known to reduce life expectancy.The average life expectancy is about 2-5 years after diagnosis.
CauseThe cause of ALS is not known.Juvenile PLS is caused by mutations in a gene called ALS2.
OccurrenceALS has an incidence rate of about 2 individuals out of 100,000 every year.PLS is known to have an incidence rate of about 1 case every 10 million people per year.
Hereditary NatureEvery individual with ALS has a 50% chance of passing on the disease to their offspring.PLS is not considered a genetic disease as most cases occur sporadically.

What is ALS?

ALS, short for Amyotrophic Lateral Sclerosis, is a progressive nervous system disease. It affects nerve cells in the spinal cord and the brain, which causes an inability to muscle control.

It is called Lou Gehrig’s disease, after the baseball player who is popularly known to have inherited the disease.

5-10% of cases of ALS have been known to be inherited. The cause for the rest is unknown.

ALS begins on a smaller scale. It could begin with muscle twitching, slurring words, or limb weakness.

It is a fatal disease known to kill within two to five years of diagnosis. It has no cure.

Symptoms of ALS vary from person to person. Some common symptoms observed are –

  • Difficulty Walking
  • Tripping and Falling
  • Weakness in feet, legs, and ankles
  • Hand Weakness or clumsiness
  • Slurred Speech
  • Trouble in swallowing
  • Muscle cramps
  • Inappropriate laughing, crying, or yawning
  • Twitching in arms, shoulders, and tongue

ALS causes motor neurons to deteriorate and eventually die. When motor neurons are damaged, they fail to send messages between the brain & the spinal cord and to the muscles throughout the body. This prevents the muscles from functioning normally.

What is PLS?

Like ALS, PLS is a progressive degenerative disease of the motor neurons.

The progress of PLS is more gradual and less devastating than ALS. Thanks to this, PLS does not shorten the life expectancy of its victims.

PLS does not result in muscle wasting. Although it is disabling, it is not fatal. Some ALS specialists also believe that PLS may be a disease on the ALS continuum and may not be a separate disease in itself. Just a slow-progressing type of ALS.

This is also because PLS has the potential to be reclassified as ALS if both upper and lower motor neurons start being affected over time.

PLS begins with stiffness and pain due to spasticity. Gradually, PLS may develop problems in balance and lower back & neck pains.

As the upper limbs start being affected, daily chores become increasingly difficult. Speech impediments start developing. Swallowing and breathing become compromised in the later stages of the disease.

No treatment slows or reverses PLS. Symptoms can be treated using drugs to reduce pain, muscle cramps, and muscle spasticity. Physical therapy can also combat joint immobility and speech therapy for those affected by facial muscles.

The age range for onset of ALS ranges from 35 to 66 years, with the median age being about 50.5 years.

Individuals suffering from PLS are advised to visit neurologists regularly to be tested for characteristic neuronal degeneration of ALS.

Main Differences Between ALS and PLS

  1. ALS affects both the upper and lower motor neurons of the person affected. PLS, being less severe, is known only to affect upper motor neurons.
  2. PLS, being a less severe disease, does not reduce life expectancy. ALS has been known to kill individuals affected about two to five years after diagnosis.
  3. The cause of ALS is unknown, with a small minority of cases being hereditary. PLS is caused by mutations in a gene called ALS2.
  4. PLS is a lesser occurring disease than ALS, affecting every 1 person out of 10 million compared to ALS’ 200 out of 10 million.
  5. The chances of a person receiving ALS from a parent suffering from the disease is about 50%. PLS occurs more sporadically.


It is important to increase awareness about these diseases. As their causes are unknown, they can affect anybody at any time.

Having basic knowledge about certain diseases helps diagnose these diseases on time. This can also lead to the treatment being started on time, which may prolong the affected person’s life expectancy in more fatal cases.

Being caught off-guard by being affected by such a disease yourself or a family member being affected can be devastating. Having more knowledge about this topic should help you to fight it better.


  1. https://www.sciencedirect.com/science/article/pii/S0896627306007252
  2. https://www.sciencedirect.com/science/article/pii/S2352340920311410
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